For a variety of reasons, it is desirable to tag migratory animals, such as fish, so that the animals can be followed or tracked over a period of time. The conventional way of tagging animals is with a visible implant tag or a fluorescent colorant. For example, Haw et al., in U.S. Pat. No. 4,750,490, use visible implant tags to identify fish. The tags are implanted into transparent or semi-transparent tissue. When the fish is captured, the location of the visible implant tags can be ascertained visually and the tags can be excised and read or read through the transparent to semitransparent tissue.
Sandstrom et al., in U.S. Pat. No. 4,392,236, disclose an animal identification system using fluorescent implanted tags coded with one or more higher atomic number chemical elements and an automated method for reading the coded information.
Ekstrom, in U.S. Pat. No. 5,324,940, discloses an electronic identification system for identifying fish by implanting tags having identification codes of fluorescent colorants in the fish. The information encoded in the tags is obtained from the tags by measuring the spectrum of light emitted by the fluorescent colorants.
Biegel et al., in U.S. Pat. No. 5,235,326, describe an electronic identification system for identifying fish. The tags are comprised of capacitors, inductors, transistors, and possibly other solid-state devices packaged in a form adapted for attachment to or implantation in a fish.
Horan et al., in U.S. Pat. No. 4,762,701, disclose a method for tracking cells in vivo by labeling the cells with cyanine dyes and detecting the cells by measuring fluorescence, absorbance, or by detecting MRI probes included in the dyes.
Zohar et al., in U.S. Pat. No. 5,076,208, disclose a method for administering compounds such as protein to fish in an aquatic medium wherein the compound is added to the medium and ultrasound is applied to the medium to enhance or effect uptake of the compound by the animal. There is no indication that any of the compounds administered is for purposes of tagging or otherwise identifying the fish.
Conventional tags are either too large to be used with small fish (2.5 cm or smaller), or they are too expensive and involved, such as genetic markers, requiring samples from parents an progeny with the need for a thoroughly trained geneticist for interpreting the results.
However, it would be particularly useful to develop a method for marking larvae or fry of salmonids or other fishes to provide a practical means of stock identification over an extensive time period. Development of a fry marking system will enable fishery managers to determine fish origins, straying rates, and other definitive marking needs for identifying groups of fish stocked as fry.
Chemical marking methods typically have disadvantages of attenuation as the fish grows, or accumulation in hard tissues, requiring lethal sampling methods. Another drawback is less than 100% retention of the chemical mark.
A useful fry marking method should include non-lethal sampling procedures and development of simple field analysis techniques. Using protein as a marker in the blood stream could eliminate some of the disadvantages of attenuation because the signal in blood can be magnified with immunoassay, such as ELISA methods. The protein is not deposited in hard tissue, but in the blood, providing a non-lethal sampling method.
Fish traditionally have been exposed to biologically active proteins either via an injection or by immersion in a bath of treatment. Comparisons of blood titer from both methods gives an indication of the efficiency of protein delivery to the fish. To deliver proteins to fish too small for injections, a bath treatment is needed.